1. Field of the Invention
The present invention relates to vehicle situational awareness display systems, and more particularly to a vehicle range display system that depicts a vehicle's position in relation to actual or virtual ground features in a speed dependent variable manner.
2. Description of the Related Art
Moving-map display systems have been used to enhance the situational awareness of the operators of ground vehicles and to assist in the movement of these vehicles along a desired route. The desired route may be specifically indicated or a general map may be provided from which the operator can distinguish the desired route. The presentation of the vehicle's position is provided on a display device and typically consists of a symbol representing the aircraft positioned on the display in relation to symbols representing the ground features surrounding the vehicle's position. The features represented may include the physical boundaries of roadways or pathways defined by paved areas, buildings or other permanent structures, natural features such as vegetation and bodies of water, signs, and markings such as roadway center stripes.
Moving-map display systems have been used to improve situational awareness including applications in ground, marine, and air navigation. A database of the desired features to be represented on the display device needs to be transmitted to the moving-map display system or be entirely encoded within the system itself. The representation of each of these features (designated in total as the “map”) is positioned relative to the symbol representing the vehicle. The designation of the system as a moving-map display system implies that when the vehicle is in motion, the vehicle symbol remains fixed on the display while the map moves so the vehicle symbol remains correctly positioned on the portion of the map (and its features) being displayed. The vehicle symbol can be fixed at the center of the display or may be biased downward if more of a forward view from the vehicle is desired.
In order to determine the relationship of the vehicle symbol to the map representation, a precise position of the vehicle in relation to a reference point on the map must be known. This also assumes that the precise position of each feature of the map is also established in relation to that reference point. Therefore, the moving-map display system interfaces with or incorporates a precise position location system, which may be a satellite based system such as the Global Positioning System or a terrestrial based system such as LORAN, that in conjunction with widely available computer processing capability can readily provide location with respect to the earth's surface.
The extent of the map presented on the display device is dependent on the scaling or range established for the total display area allotted to the moving-map representation. The moving-map display range is set as appropriate for the application which the moving-map display system supports. Typically, the moving-map display system includes a “zoom” feature which allows the range of the presented map to be reduced (zoom-in) or expanded (zoom-out) in discrete steps through manual selection by the operator.
While a manual selection of discrete moving-map zoom settings may be adequate for certain vehicle movement applications, larger vehicle movement applications, such as the taxiing of large aircraft, rely on sufficient anticipation of required changes in vehicle movement (e.g., upcoming stop positions, turns) as well as the ability to determine how well a particular maneuver is being accomplished (e.g., closeness to required stop position, closeness to turn center). Specific moving-map zoom settings may not be adequate to support all of these maneuvering tasks. However, certain vehicle maneuvers (e.g., stopping and turning) may require full attention of the vehicle operator(s) and, therefore, may not allow an opportunity to manually alter and optimize the moving-map display zoom setting.
U.S. Pat. No. 6,571,166, issued to W. A. Johnson et al discloses a head up display system that incorporates conformal and non-conformal views and associated symbology to provide highly informative and intuitive guidance with respect to all aspects of operating an aircraft or other vehicle in a controlled geographical area, by utilizing calculated views from the pilot seat, aircraft speed, and relevant ground operation information. The non-conformal view incorporated in that invention is related to a moving-map display type feature in that it provides route information which cannot be directly viewed within the real world features as seen through the head up display. However, that invention's display of geographical information is limited by the maintaining of a relatively consistent presentation between the non-conformal and conformal views. While this allows adequate close range awareness at slow aircraft ground speeds, it is deficient in providing longer range awareness of upcoming turns and stop points.